The key question is: does converting a Fujifilm raw file in ACR delivers the same look and feel as an in-camera JPEG using the same film simulation? In Adobe Camera Raw, film simulations are found in the Camera Calibration area as shown.

My motivation here was to establish equivalency (or non-equivalency) before proceeding with further image processing of Fujifilm X-Pro2 files.

John M writes:

This is absolutely fascinating, Lloyd. I wish I could fly you over here to see what happens on my setup. There is a small but distinct difference between on camera and ACR converted images. But I don’t have an X-Pro 2. I have a X-T1 and a X-100T. So I wonder if it is something that has changed with the new generation of sensor or JPEG engine or whether there is some obscure LR setting that I have wrong.

DIGLLOYD: I can only show my own meticulously prepared results from the XPro2—the camera I have and the workflow I do. All settings must match up of course. Easy to make an error there. Remember too that the choice of things like sharpening level can alter perception, and sharpening cannot be matched in ACR to what the camera does.

Fujifilm’s best and fastest processor is in the X-Pro2. It is quite possible that older models have less good processing due to limited CPU speed and/or certain other processing algorithm choices. Even JPEG compression could be a factor, since better JPEG results require more CPU power, so it is possible that the XPro-2 JPEGs are improved.

But the likely main source of a discrepancy is color gamut; in-camera JPEGs offer only sRGB or AdobeRGB color spaces. When color is out of gamut, the camera has to map those unreproducible colors (somehow) to other colors. At the least, when comparing in-camera JPEGs to raw-derived JPEGS, those JPEGs must be in AdobeRGB color space (not sRGB, since sRGB destroys saturated reds and greens and blues). For my comparison, I converted in ACR to 16-bit ProPhotoRGB, then promptly converted to AdobeRGB (since all the camera can do is AdobeRGB).

Since out-of-gamut colors can be mapped by algorithms that differ by camera model and firmware version, the results could vary by camera—gamut mapping has a variety of approaches; it is not one fixed thing (see all the options in Photoshop for example). In particular, a recent interview with Fujifilm over at imaging-resource.com discloses that Fujifilm has improved the gamut mapping. Which is great but a band-aid: why not offer a superior gamut in the first place (like the DCI P3 gamut), so that color does not have to be mangled? Computers like the late 2015 iMac 5K have a gamut well beyond AdobeRGB in the reds.